Water pollution has become a severe challenge in China in recent years. On the one hand, water shortage has become one of the main constraints for the development of China Mid-west and China North, and deep treatment of municipal sewage and industrial wastewater are in great demand to increase utilization rate of reclaimed water; on the other hand, issues about drinking water safety have turned increasingly serious, with more and more bio-toxic organic pollutants in trace amounts being found in water bodies. In response to this situation, China Ministry of Health [now called “National Health and Family Planning Commission”] and China Standardization Administration jointly revised the “Standards for Drinking Water Quality” (GB5749-2006), increasing the quality indicators from 35 items to 106 items. This new “National Standards” took effect on Jul. 1, 2007. Its implementation means higher standards are required to guarantee the drinking water safety. Accordingly, many conventional processes for supplying drinking water cannot meet the new standards. New economical yet effective methods for deep purification of water are in great demand.
Resin adsorption is one of the commonest techniques for water deep treatment. The ion exchange resin can remove pollutants in water by adsorbing them onto its surface through electrostatic attraction. It exhibits considerably high efficiency in removing various recalcitrant substances and trace pollutants. In comparison with other techniques for water deep purification, the ion exchange process exhibits many advantages, such as good purification effect, low operational cost, moderate investment amount and simple operating procedure. However, when being put into practical application, a certain amount of desorption liquid will be generated. The constitution of the desorption liquid is very complex; it usually contains high concentration of organics and salts, and presents high chromaticity and poor biodegradability.
The common methods to dispose desorption liquid include solidification and burial, evaporating condensation and incineration, and advanced oxidation. The method of solidification and burial involves merely displacement of pollutants and it usually takes up substantial land resources. On the contrary, a thorough treatment can be obtained if the desorption liquid is firstly treated with evaporating condensation and then incineration; however, the evaporation process consumes a large quantity of energy and therefore pushes up the production cost. Another widely-used method for treatment of desorption liquid is advanced oxidation, during which desorption liquid undergoes various advanced oxidation processes before being channeled to a municipal sewage treatment plant for further treatment. The advanced oxidation can be realized through various processes, such as ozone oxidation, Fenton oxidation, electrocatalytic oxidation; these processes can achieve desirable effect in treatment of desorption liquid. However, as there exists a considerably large quantity of desorption agent in the liquid, it would be on the one hand a waste of resources if the desorption agent is not effectively separated out and put into reuse, and on the other hand bring about adverse influence upon the final treatment of the municipal sewage. Therefore, in order to further tap the potential of the resin ion exchange process in water deep purification, a new method for economical yet effective treatment of desorption liquid is urgently required.
The composite iron enzymatic activated sludge process involves the enhancement of microbial activity with the iron ion. The iron ions participate in electron transfer reaction and can act as the activator for the enzymatic reaction by means of mediating biochemical reaction of microbes and their energy metabolism. It can enhance metabolic activity of microbes and improve the flocculent structure of activated sludge, which consequently enhances microbes' tolerance against environmental change. However, insofar as the field of desorption liquid treatment is concerned, no documents have been disclosed in transforming desorption liquid into the nutrient solution for the composite iron enzymatic activated sludge.
The membrane separation is a widely-used technique for separating substances as it is only a physical process and involves no new substance or phase change. The pore size of the membrane is usually at micron scale. According to the specific size (also called “molecular weight cutoff or MWCO”) of membrane pores, the filtration membrane can be divided into microfiltration membrane, ultrafiltration membrane, nanofiltration membrane and reverse osmosis membrane; according to the material of membrane, it can be divided into inorganic membrane and organic membrane; the inorganic membrane is mainly made of ceramic and metal. Currently, the membrane separation technique is widely adopted in beverage industry, food industry, pharmaceutical industry, seawater desalinization, preparation of pure water or ultrapure water, and wastewater treatment. When being used in the wastewater treatment field, it is mainly adopted to realize deep treatment and recycled use of lowly-concentrated water that has undergone the secondary treatment. The membrane separation technique is rarely used to treat the highly-concentrated wastewater.
As there exist high concentration of organics and the regeneration agent in the resin desorption liquid, skilled personnel in the field of desorption liquid treatment have long been designing new methods to separate out organics and the regeneration agent from the desorption liquid, which can simultaneously realize innocent treatment of the desorption liquid and resourceful utilization of organics and the regeneration agent.
To those skilled in the art, it is a constant challenge how to effectively integrate the composite iron enzymatic activated sludge process and the membrane separation technique together so as to realize resourceful utilization of highly-concentrated organics and the regeneration agent contained in the resin desorption liquid.